It is hard to imagine a video hard fitting in the small PCIe slot of the TS-453B. This NAS already has an HDMI 1.4B port. This allows for 4K but only at 30 frames per second. But if you want a higher frame rate at 4K, I think it makes sense to stream to another device to play the video.

I like streaming because it is easy to play video on any device and even when I am away from home.